If I resigned from my job and was travelling, should I put travelling or unemployed in the n 400 form?

Yes, you indicate unemployed if you were not employed.

Adjustment of Status While I-130 is pending

Yes, you can interfile the adjustment if your I-130 priority date/final action date is current.

Yes, but it needs to meet the USCIS poverty guidelines, look at the guidelines here: https://www.uscis.gov/i-864p

It refers to the passport you used to enter the US the last time you entered.

COS (H4-F1) Age-out situation

You don't have a clear solution, thats why you are getting different answers. I also vote with listening to your attorney A, and also extending...

Apply for H4 when I140 approved and H1 denied through counslar process ?

you can apply for H4 even if you have an immigration process pending. what is HNSC? An H1B denial for you (not the principal of the H4) should...

How soon should we file I-130?

No, you can file after you marry, you don't have to wait.

Just got an approval for the i130 from NBC i filed for my wife when i was PR ? now i am a citizen what next

Either file her adjustment of status in the US with proof you are a citizen or notify USCIS and ask them to notify the NVC if she is processing it...

What would be the status of an F1 student in case of the concurrent filing of EB2-NIW, i-765 is approved but i-140 denied later?

Could reactivate the H1B by traveling and reentering on valid H1B visa if still employed by the H1B employer. The F-1 is out of status and may not...

What is my status if my job terminates from company A while my employment with company B starts at a later date ?

Employer will file change of employer/extension petition with a particular start date and while the petition is pending you are in lawful status. ...